2023 04 17

2023-04-17¶

Slick Join¶

예시 테이블

case class Person(id: Int, name: String, age: Int)

class PersonTable(tag: Tag) extends Table[Person](tag, "person") {
    def id = column[Int]("id", O.PrimaryKey)
    def name = column[String]("name")
    def age = column[Int]("age")

    def * = (id, name, age) <> (Person.tupled, Person.unapply)
}

case class Address(id: Int, street: String, city: String, state: String, zip: String, personId: Int)

class AddressTable(tag: Tag) extends Table[Address](tag, "address") {
    def id = column[Int]("id", O.PrimaryKey)
    def street = column[String]("street")
    def city = column[String]("city")
    def state = column[String]("state")
    def zip = column[String]("zip")
    def personId = column[Int]("person_id")

    def person = foreignKey("person_fk", personId, TableQuery[PersonTable])(_.id)

    def * = (id, street, city, state, zip, personId) <> (Address.tupled, Address.unapply)
}

Join 해보자

val query = for {
    (p, a) <- TableQuery[PersonTable].join(TableQuery[AddressTable]).on(_id === _.personId)
} yield (p.name, a.street, a.city)

val result = db.run(query.result)

왜 for-comprehension을 쓰는거지?
- concise and readable 하기 위해서 임
- (p, a) <- TableQuery[PersonTable].join(TableQuery[AddressTable]).on(_id === _.personId)
  - 여기서...
    - p = PersonTable
    - a = AddressTable
  - yield...
    - 열심히 조인해서 어떤 튜플 가져올지?!
      - (p.name, a.street, a.city)
  - join 해서 결국 가져올 칼럼 깔끔하게 쓸 수 있음

Pagination은?

단일 테이블에 대해서 페이지네이션

val pageNumber = 1
val pageSize = 10
val offset = (pageNumber - 1) * pageSize

val query = TableQuery[PersonTable].sortBy(_.id).drop(offset).take(pageSize)
val result = db.run(query.result)

join 하고 난 뒤 페이지네이션

val pageNumber = 1
val pageSize = 10
val offset = (pageNumber - 1) * pageSize

val query = for {
  (p, a) <- TableQuery[PersonTable].join(TableQuery[AddressTable]).on(_.id === _.personId)
          .sortBy(_._1.id)  // 여기서 _1 는 튜플의 첫 원소를 말함. 여기서는 p를 뜻한다
          .drop(offset)
          .take(pageSize)
} yield (p.name, a.street, a.city)

val result = db.run(query.result)